It is known that stem cells migrate toward sites of pathology. Recently, it was found that bone marrow-derived mesenchymal stem cells (BM-MSCs) have a tropism for tumors and migrate toward tumor sites. Such BM-MSCs that can migrate to sites of specific tumors may prove to be a useful tool in gene therapy. For example, BM-MSCs having a tropism for tumors can be used as vehicles for transferring a therapeutic suicide gene to tumor sites [see Ponte A. L. et al., Stem Cells, 25, 1737-1745 (2005); Kahler C. M. et al., Respir Res 8, 50 (2007)]. Despite this interesting phenomenon, the molecular mechanisms regulating MSCs trafficking to tumor are unclear.
Growing evidence over several years indicates that induction of BM-MSCs migration seems to be stimulated by several soluble factors. Recently, monocyte chemoattractant protein-1 (MCP-1) secreted from breast cancer cells has been shown to stimulate BM-MSCs migration [see Dwyer R. M. et al. Clin Cancer Res 13, 5020-5027 (2007)]. Furthermore, chemokine ligand2 (CCL2) and chemokine ligand10 (CCL-10) can induce the migration of neural progenitor cells to sites damaged within the middle cerebral artery occlusion (MCAo) stroke model [see J Neurosci Res 85, 2120-2125 (2007)]. An insulin-like growth factor-1 (IGF-1) markedly increased the rat BM-MSCs migratory response [see Li Y. et al. Biochem Biophys Res Commun 356, 780-784 (2007)]. Therefore, identifying the soluble factors that affect migration events of MSCs is important for understanding how MSCs migrate toward tumors or damaged tissues.
Genes introduced to BM-MSCs are over-expressed in vivo and show bioactivity. For example, BM-MSCs to which a human hAng1 gene is introduced stimulate generation of blood vessels in an infarction site of an acute myocardial infarction model animal [see Sun L. et al., Biochemical Biophysical Research Communication 357 (2007) 779-784], BM-MSCs overexpressing Akt surprisingly treat myocardial infarction and improve functions of heart [see Nicolas N. et al., Molecular Therapy 14(6), 840-850, 2006], Bcl-2 gene-modified BM-MSCs prevent apoptosis and improve functions of heart [see Stem Cells 25, 2118-2127 (2007)], and BM-MSCs overexpressing endothelial nitric oxide synthase recovers the damage of right ventricular caused by pulmonary hypertension [see Sachiko et al., Circulation, 114[suppl I]:I-181˜I-185]. These results indicate that MSCs to which genes are introduced can be used as a tool in gene therapy.
Meanwhile, in general, cells of the central nervous system are well regulated, wherein the central nervous system consists of a brain and a spinal cord. However, when this regulation collapses, cells are continuously divided and tumors are formed. Tumors can be categorized as benign tumors or malignant tumors. The central nervous system has neurons, and glia cells that support and protect the neurons. Tumors generated in glia cells are known as glioma. Glioma accounts for 50% of primary brain tumors and accounts for 15% of primary spinal cord tumors. In addition, brain tumors include neural tumors, blood vessel tumors, and gland tumors. There is also a secondary brain tumor caused by other tumors developed in other sites of the body. The secondary brain tumor is the most common type of brain tumor
Treating brain tumors are difficult due to the sites of the tumors. Brain tumors can be treated by physical surgery or chemotherapy. For physical surgery, when tumor sites are completely removed, complications are likely to occur. For chemotherapy, a high-concentration anticancer drug needs to be injected due to a brain-blood barrier, and thus, it seriously damages other organs. Recently, gene therapy has been used to treat brain tumors. In gene therapy, a gene is introduced for suppressing growth of cancer cells by using a virus vector. Since the virus vector does not have a selective migration capability toward a target cancer site, the virus vector is surface-modified to obtain such capability. However, there is a limit to migrate a sufficient amount of virus vectors to the target cancer site.
Research results on a homing effect, which is a phenomenon in which stem cells migrate toward a disease site, have been disclosed, indicating that stem cells can be useful delivery media for treating brain tumors. However, mechanisms regulating stem cells trafficking to tumors are unclear. It is known that neural stem cells have a tropism for a type of brain tumor, that is, malignant glioma. Based on this theory, research into a method of transferring genes to a brain tumor site by using neural stem cells that function as a vehicle is being conducted (see Yip S et al., The Cancer J 9(3), 189-204, 2003; Kim S K et al., Clin Cancer Res 12(18), 5550-5556, 2006). Yip et al. found that brain tumors can be treated with neural stem cells carrying an immune regulatory gene, an apoptosis promoting gene, a pro-drug converting enzyme, an oncolytic virus, etc. Brown et al. identified that brain tumors can be effectively treated by injecting a cytosine deaminase gene-containing vector into the brain, wherein the cytosine deaminase gene changes 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU), wherein 5-FU is an anticancer drug and 5-FC is a prodrug of 5-FU (see Brown A B et al., Human Gene Ther. 14(18), 1777-1785, 2003). Ehtesham et al. reported that growth of brain tumors was decreased by injecting neural stem cells treated for delivering interleukin-12 or a tumor necrosis factor-related apoptosis-inducing ligand (Cancer Res 62, 5657-5663, 2002; Cancer Res 62, 7170-7174, 2002). However, using neural stem cell in clinical experiments causes ethical problems related to how neural stem cells are taken, and immunological rejection caused by allogenic transplantation. Accordingly, there is a need to find other types of stem cells that do not cause these problems and can be easily obtained.
Akira et al. disclosed that BM-MSCs have a tropism for brain tumors (see Cancer Res 65(8), 3307-3316, 2005). BM-MSCs can be taken from patients. When BM-MSCs are injected through autologous transplantation, immunological rejection does not occur, which is an advantage for a clinical use. In a study, human BM-MSCs were injected into nude mice having skulls transplanted with human glioma cell lines through a carotid artery. As a result, the human BM-MSCs were found only in glioma and not in a normal part of the brain adjacent to glioma. In addition, even when human BM-MSCs were transplanted into a skull, human BM-MSCs migrated toward glioma. When human BM-MSCs were infected with an adenovirus vector containing cDNA of an IFN-beta gene and then the resultant vector was injected into a glioma-transplanted skull of a nude mouse through a carotid artery, the lifetime of the nude mouse was increased. WO07/037,653A1 discloses a composition for treating cancer, comprising BM-MSCs expressing a cytosine deaminase gene. In this case, however, since BM-MSCs are taken through a plurality of complex processes, subjects from which the BM-MSCs are taken suffer from mental and physical stress for a long period of time. Accordingly, there is a need to find other types of stem cells.
Unlike bone marrow, umbilical cord blood (UCB) having many MSCs can be easily taken from umbilical cords which were discarded in delivery processes. Also, the UCB storage industry is well established and thus, it is easy to find donors. Even when MSCs taken from other human-induced UCB are used, immunological rejection does not occur after transplantation. Accordingly, high immunological stability can be obtained. Therefore, it is very important to identify whether a disease such as a brain tumor can be treated based on tropism of UCB-MSCs. However, such attempts for identifying availability of UCB-MSCs have not yet been made. All the references cited in the present specification are incorporated by reference in their entity. Also, all the information disclosed in the present specification is used only to help understanding of the background of the present inventive concept and cannot be prior art.